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Data Protection

What we do — and don't do — to protect data stored on our systems.

Disk storage

All of our critical servers use RAID (Redundant Array of Inexpensive Disks) to improve reliability. This allows the loss of at least one hard disk without any data being lost. In many cases the disk can be replaced and the array rebuilt without the system ever being shut down.

Data backups

Policies

All user data stored on our servers is backed up. Generally backups are run nightly, with the exception of bimonthly full backups, which can take up to three days to complete due to the volume of data involved.

Limitations

Currently there are no off-site backups. Backups are stored on campus, although they are in a different building. This means a widespread disaster could destroy both the original data and the backup.

User responsibilities

Because of the lack of off-site backups, you should retain your own copies of any data you cannot afford to lose. We highly recommend that you store these copies off campus, to minimize the chances of them being destroyed should a natural disaster affect the UW campus. Remember, we live in an area where severe and sudden geological hazards exist.

After the Northridge earthquake, some researchers at California State University-Northridge lost their life's work when buildings burned down or were contaminated by hazardous materials. Don't let this happen to you!

If you need assistance in determining the best way to package up your data for downloading or transfer to other media, email linghelp@u.

Data restoration

If you accidentally delete or overwrite an important file, you can ask to have it retrieved from backup. Note that backups are mainly meant as a way of recovering a failed server, and are not an archival system or a substitute for version control! They may expire in as little as two weeks, depending on disk space needs.

Requesting file restoration from the backup server

Email linghelp@u to arrange to have a file retrieved from backup. Entire directory trees can be restored if necessary. Please provide enough information to identify the correct version of the file, if it has been overwritten; for example, the approximate modification date and/or size. Keep in mind that any changes since the most recent backup cannot be recovered.

Self-recovery

Advanced users may want to try retrieving the file themselves from a snapshot, especially if it was just overwritten or deleted recently.

Our backup system works by creating a shapshot of the state of the filesystem, then transferring the contents of the snapshot. To create a point of reference for incremental backups, it generally retains one snapshot for the most recent biweekly full backup, and one for the most recent nightly incremental. As a side effect, this gives two restore points that are accessible to users.

To access these snapshots, you need to go into the ~/.zfs/snapshots directory. (Note that .zfs is hidden from ls, even ls -a.) Each subdirectory of snapshots is a read-only view of your home directory as it appeared when the snapshot was taken. They do not represent all the backups that are available, however, so if you don't find what you need, feel free to email linghelp@u to see if it can be retrieved.

Topic revision: r3 - 2011-09-09 - 18:11:06 - brodbd
 

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